In commercial container filling or packaging operations, the containers typically are moved by a conveying system at very high rates of speed. Typically, lubricant compositions are applied to the conveying system to permit high-speed operation of the conveyor and limit marring of the containers or labels. Lubricants can be “wet” lubricants or “dry” lubricants.
Wet lubricants refer to a concentrated lubricant that is diluted with water to form an aqueous dilute lubricant solution (i.e., dilution ratios of 100 part of water to 1 part lubricant up to 500 parts of water to 1 part lubricant), and copious amounts of aqueous dilute lubricant solutions are applied to the conveyor or containers using spray or pumping equipment. These lubricant solutions disadvantageously require use of large amounts of water on the conveying line, which must then be disposed of or recycled, and which cause an unduly wet environment near the conveyor line. Also, variations in the water can have negative side effects on the dilute lubricant solution. For example, the presence or absence of dissolved minerals and alkalinity in the water can cause an unacceptably high coefficient of friction between lubricated surfaces and poor lubrication.
When an aqueous dilute lubricant solution is used, it is typically applied at least half of the time the conveyor is running, or applied continuously. By running the aqueous dilute lubricant solution continuously, more water and more lubricant are used, and the lubricant concentrate drums have to be switched out more often. Much of the dilute aqueous lubricant solution runs off of the conveyor surface and is wasted and furthermore drip pans are required to collect waste lubricant solution and carry it to the drain.
A limitation with aqueous dilute lubricant solutions is that when the lubricant spray ceases, COF values increase rapidly and thus conventional aqueous lubricants are applied in a continuous or nearly continuous fashion. It is believed that the COF values increase when the aqueous lubricant drains from the conveyor surface because the lubricating liquid film between surfaces in sliding contact is substantially water. The relatively rapid draining of the aqueous lubricant composition severely limits the period of non-application time.
“Dry” lubricants refer to lubricant compositions that are applied intermittently to a container or conveyor without dilution. However, this application typically required special dispensing equipment such as energized nozzles. Energized nozzles refer to nozzles where the lubricant stream is broken into a spray of fine droplets by the use of energy, which may include high pressures, compressed air, or sonication to deliver the lubricant. Silicone-based dry lubricants have been described that do not require special dispensing equipment and can be applied using non-energized nozzles. However, silicone is primarily effective at lubricating plastics such as PET bottles, and has been observed to be less effective at lubricating on glass or metal containers, particularly on a metal surface.
It is against this background that this present disclosure is made.